Casey Affleck Recalls Joint Birthday Parties With Older Brother Ben Affleck (Exclusive)

Casey Affleck is gearing up for his birthday on Aug. 12 -- which is just three days before his big brother, Ben Affleck , celebrates his own birthday -- and he's looking to reclaim the day after years of sharing the spotlight.

Casey walked the red carpet at the New York Premiere of his new film The Instigators at Jazz at Lincoln Center on Wednesday, and he spoke with ET's Rachel Smith about his upcoming 49th birthday -- and how he always had to share the festivities with Ben as a kid.

"We had to, all growing up," Casey explained. "We got one birthday party between the two of us."

So is that a tradition that they've kept going into adulthood? According to Casey, "Not so much."

"Once we had kids, like, my birthday became not so important, you know? And it was always about them," he explained. "But now that they're moving out of the house, maybe I should reclaim that...[This year] I'm throwing myself a birthday party!"

Casey, who is currently in a long-term relationship with actressCaylee Cowan , shares two sons with his ex-wife,Summer Phoenix -- 20-year-old Indiana and 16-year-old Atticus.

Ben, meanwhile, shares three children with ex-wife Jennifer Garner -- 19-year-old Violet, 15-year-old Seraphina and 12-year-old Samuel.

Looking toward the future, with his birthday around the corner and the big 5-0 next year, Casey says he wants to continue to challenge himself when it comes to his work.

"I really just want to keep working with people I love and some people I've not had a chance to work with, but focus less on trying to climb the ladder, trying to achieve things, and focus more on personal work and my own challenges that I want to work on and work with people I like and have a good time," he explained. "[I'm interested in] seeing if I can dig deeper into being a writer and a director and actor and see what else is out there -- before it's all gone and it's all AI and TikTok."

It's for this reason that The Instigators proved to be such a fruitful and rewarding project for Casey.

Not only does he star in the film -- opposite longtime friend Matt Damon and his own girlfriend, Caylee -- he also co-wrote the screenplay withChuck Maclean, and got the chance to shoot the film in Boston, where the crime caper takes place

"I'm not gonna lie, I've been doing this for 38 years and had a lot of ups and downs and I worked hard -- but still, when I was standing on set, I felt really lucky, you know?" Casey shared. "It's in my hometown, working with people I love, working with new people I'd admired for a long time, doing what I like to do and making a living."

"So, you know, [I was just] waiting for someone to wake me up," he added.

The Instigators -- co-starringHong Chau, Paul Walter Hauser, Michael Stuhlbarg, Ving Rhames, Alfred Molina, Toby Jones, Ron Perlman and Jack Harlow, and directed by Doug Liman -- hits select theaters Aug. 2, before dropping on Apple TV+ Aug. 9.

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